Pulmonary edema, a medical emergency, is an accumulation of fluid in the lungs. Pulmonary edema is often caused by congestive heart failure. When the heart is not able to pump efficiently, blood can back up into the veins that take blood through the lungs.
As the pressure in these blood vessels increases, fluid is pushed into the air spaces (alveoli) in the lungs. This fluid reduces normal oxygen movement through the lungs. These two factors combine to cause shortness of breath.
Failure of the left side of the heart (left ventricle) causes blood to accumulate in the veins of the lungs (pulmonary veins), producing a dangerous rise in blood pressure within these veins. Sustained high pressure in the pulmonary veins eventually forces some fluid from the blood into the interstitial space and eventually to the surrounding microscopic air sacs (alveoli), which transfer oxygen to the bloodstream. As the alveoli fill with fluid, they can no longer provide adequate amounts of oxygen to the body.
Symptoms, especially severe breathing difficulty, develop over the course of a few hours and may be life-threatening. Although the outlook for pulmonary edema is favorable if the underlying disorder is treated in a timely fashion, the overall outcome for the patient depends upon the nature of the underlying disorder. Adults at high risk for heart failure are most commonly affected.
Typical treatment for patients presenting with pulmonary edema as a result of CHF is the administration of diuretic drugs, designed to reduce preload, which is described as the mechanical state of the heart at the end of diastole, the magnitude of the maximal (end-diastolic) ventricular volume or the end-diastolic pressure stretching the ventricles. In addition, vasodilation drugs are administered so as to reduce afterload—or the pressure against which the ventricle ejects blood.